I love to read the big "blockbuster" best-seller YA and middlegrade series and try to figure out what makes them tick. Why is "Twilight" or "Harry Potter" a phenomenon? What put "The Princess Diaries" in the NY Times number one spot? Why do kids write Rick Riordan every day to tell him that Percy Jackson changed their lives? Of course there's no one answer. The thing that makes a book go super nova may be as mundane as the publisher's promotions budget or as esoteric as tapping into a zeitgeist-- the book hit at the right cultural moment. But I think there are certain things that flip a YA reader's switch, and my theory is that one of them is this: the protagonist has to have an "enviable problem." Are you in love with a vampire who is driven to kill you (Twilight)? That's a problem. Is he also gorgeous, ageless, drives a porche and has a psychic sister who can predict the stock market? That's an enviable problem. The darkest wizard the world has ever known wants you dead (Harry Potter)? Problem! You're a hero to a secret magical subculture and a legacy kid at a school for magic? Enviable problem. Does every monster in the Greek myths want to eat you (Percy Jackson)? Too bad. Is it because you're dad is secretly the god Poseidon, and you can now control the waters and command flying horses? A problem anyone would envy.
The tricks are this: First, the problem and the enviable aspect must be inseparable. You can't have one without the other. Don't give your protag a killer problem, and them give them something cool and enviable in some other, unrelated aspect of their lives. It just won't work. Second, and MOST IMPORTANTLY, your protag can not revel in the enviable aspect of the problem. Harry Potter is never fully thrilled with his celebrity in the magical world. Bella Swan doesn't care about money or fancy cars. Percy Jackson may have a moment of feeling that it's cool to control the tides, but he's ambiguous and conflicted in his relationship with his divine father. The list goes on. The thing is, if your protag digs the enviable aspect of their problem too much, it will cancel out the negative part of the problem. The stakes will become too low, the reader won't care, and the story will jump the shark because it reads as wish fulfillment. More importantly, if the protag enjoys the perks too much they are claiming those perks for themselves-- and in effect taking them from the reader. As long as Bella Swan doesn't enjoy that new Ferrari Edward bought her, I can enjoy it. But if she starts to brag about how great her car is, it's not mine to enjoy any more. She has become someone I envy rather than someone I'm living through vicariously and so she has lost some of my sympathy.
This theory mainly works for fantasy YA (and there are many fantasy blockbuster YA novels) but also works with some non-fantasy that has a high wish-fulfillment aspect (Meg Cabot's Princess Diary series, Teen Idol, All American Girl, etc.) Of course it doesn't apply to everything, but I still think it's a fun game to play. Any thoughts?